Ultraviolet light absorbing film



Och 1952 H. B. FREYERMUTH ETAL 2,514,940

I ULTRAVIOLET LIGHT ABSQRBING FILM Filed Dec. 31, 1948 so I 0.|

7o Guryes showing the relationship of castlng pH to transmission for falls of 2,4;dlhydroxybpnzophenone-5- sulfomc acld sodlum salt 0.2 so

Concentration I092, in Poly Vinyl Alcohol ,3- (D 5 Thickness O.l mm g 50 2 0.3

iu .2 g i a g pH=5.0 pH=9.45 0. 4o 0.4

I 0.6 20 or! 0.9 l0 L0 j L5 0 J 2.0 220 260 300 340 380 400 420-440 460 500 Wavelength in Millimicrons INVENTOR William 0. Ney

BY Harlan B. Freyermuth Patented Oct. 21, 1952 Harlan B. Freyermuth and William 0. Ney, Easton, Pa assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Application December a1, 1948, Serial No. 68,624

8 Claims. (01. 106-125) This invention relates to ultraviolet light absorbing films. 7

It is well known that colored objects such as dyed textiles and the like fade when exposed for prolonged periods to the effect of sunlight. Plastic materials of both the water-soluble and water insoluble type such as gelatin, polyvinyl alcohol, cellulose acetate and the like become colored, usually yellowing, and sometimes brittle and many eventually deteriorate upon exposure to sunlight. The present invention is concerned with ultraviolet light absorbers for the water soluble film forming materials which may be used themselves in packaging, as for example cellophane, or which may be used as a coating upon other materials which fade or deteriorate insunlight. The absorption of ultraviolet light in materials such as cellophane is particularlyimportant because of the wide spread usesof cellophane as a packaging material, allowing fading or deterioration of the goods which the package contains.

To be most effective, the absorber should be capable of absorbing substantially all of; the ultraviolet light within the Wave length range 200 to 400 millimicrons and even into'the visible range as high as 4.40 millimicrons.

It is a further object of the present invention to provide a film cast from a water solution of a water soluble film forming plastic containing a Water soluble compound particularly adapted to absorbing light having a Wave length above about 400 millimicrons.

These and other objects are attained by the present invention wherein a film is cast from a water solution of a water soluble film forming plastic containing a compound having the following general structure:

OHv

wherein one B is hydrogen and the other R is an alkaline sulphonate radical.

We have discovered that these compounds when combined with a water soluble plastic in acqueous solution having a pH in the range to 9.5 are unexpectedly compatable and do not crystallize out or make an opaque film as might be expected but rather form a clear film which has the desired light absorption.

The sulphonic acid is neutralized with any of various alkaline material including alkaline earth metals, ammonia, amines such as aliphatic, aromatic, cycloparafiinic and heterooyclic amines, and preferable alkali metals, alkali hydroxides,10r alkaline alkali metal salts (e. g. NazCOal. The'following compounds are illustrative:

and preferably:

'It is an important element of the present in;- vention that the compound have a pH in the range of 5 to 9.5. The above compound, for example, in acid form has a pH of about 1.5

a and is unstable and absorbs very-littlei light above 390 millimicrons. v

The following examples will serve to illustrate the invention and are preferred embodiments thereof, but are not intended to limit the 'invention. EwampleI 43 parts of 2,4-dihyd ox benzophenone was added to 200 parts of 29% oleum at a temperature of about 1520 C. and allowed to stand for about hr. The mixture was added to 1,500 parts of ice whereupon the sulfonated product began to separate out. The mixturewas then re dissolved by heating 'to 35 C. and stirred with 5, parts 'Nuchar and15 parts filter cell (commercial clarifying agents). After filtering, 1000 parts, of, a saturated sodium carbonate solution was added. The sodium salt, of 2,4-dihydrox-yv .benzophenone -.5 sulphonic acid precipitated,

Example 2 Ten parts of the sulphonic acid product of Example 1 was dissolved by heating in parts like.

of water to 80-90 C. To this solution was added an equiyalent amount of an aqueous solution of cyclohexyl amine. On cooling, the cyclohexyl amine salt of 2,4-dihydroxybenzophenone precipitated as large, nearlycolorless plates (pH of acteristic of absorbing light .in the ran e 2 20 7 to 430 millimicrons.

To 90 parts of a 10% aqueoussolution of gela-'- tin was added 1.0 part of the sodium' salt of 2,4-dihydroxybenzophenone-5-su1fonic acid. AA film resembling thatthe Example 1 was obtained.

Example 4 T0730 ;parts .of af1I0%" solution of gelatin. was

aiided-1.0. part-of-cyclohexyl amine-salt of' 2,4-

dihy'drQXybe ZQDhenone-S-sulfonic .acid. A film resembling that of .iExample ".2 was obtained. The graph shown in the drawing'i's self-explanatory. It-demonstrates that the compounds of the present invention absorbsubstantially all of the ultraviolet light without extending substantially into the visible range and shows the 'efiect of the pH o'nthe absorption characteristics of these compounds. I p

The film of' the present invention may be a self-supported film such as the cellophane used in packaging or it may be used as a protective coating on other bases such as water soluble or water insoluble plastic materialsas, for example, photographic cellulose acetate film, glass or the The compounds of the present invention are cclorlessandj s such absorb very little visible .lig ht-and subsequently do not distort thecolor balance of articles which they may protect. They are useful in photographic .filters sun tan lotions, vand cellophane potato chippackages, .among other uses. 3 Y

The compound ofExample 1 contains :the sul- -Ionic acid group in the substituted :tresorcinol) ring-because onloxidation, benzoic .acid is isolated from the reaction products, which demonstrates that sulfonation doe-snot take place in the other ring.

' Examples of "film-forming "organic plastic mater-ials which are soluble in the aqueousmed'iums "hereinemp'loyed,-that is aqueous mediums h-aving -a pH in the range-o-f 5 to 9;5 include regencellulose,- partially hydrolyzed polyvinyl "acetate, polyvinyl alcohol, elatin, carboxymethyl' cellulose, hydroxyxn'thyl cellulose, urea-formaldehy'de resins, melamine iormaldhyde resins,

polyvinyl-methyl ether, eta: I Cont'rol-of the pl-Iof thecompound'orthe pr es- [file of this patent:

ent invention to keep it in the range pH 5 to 9.5

is important for substantial absorption to 400 to 440 millimicrons and the pH within those limits is substantially proportional to the Wave length of light absorbed within the range, indicated. Thus the material absorbs substantially all of the light below :the visual range whileritself being colorless .or veryipale yellow.

It will be understood that the amount of these compounds used will depend upon the thickness of the supporting film and the pH. In general the higher the pH-and the larger the amount of compound the more the curves will extend toward the :visible range. At a pH of 5.0 for example,

pound per cm; gives satisfactory absorption.

We claim: '1. An 'improvedultraviolet light absorbing film comprising a film-forming plastic soluble in an aqueous medium having a pH of 5 to 9.5 and a salt :of a .sul-fonic :acid, which sulfonic acid has the formula: v

wherein orient the radicalsR ,andiR" 'isfhydrovgenand the otheri-s ISOa'H, said salt having am in aqueous .solutionilinthe range "5 to 925.

2. The film of claim .1 .wherein'R 'is'hydrogeli, RCisan orithoesOs'H radical in the mated-struc- .tural liormula, and the .salt a .sodiumsalt.

3.. The'film of claimil wherein R ishydrogen, .Ris an SOaH.radica1 in the..5 position ,inthe recited structural .formula, and the salt isla sodium salt. Q I

4. The .of claim ,1 wherein ,the said .film- [forming plastic is regenerated cellulose. 1

5. The film of claim 1 wherein the said fihnforming plastic .is polyvinylalcohol. Y

.6. The film-of .c-laiml wherein the said .film- -f.orming.plasticis gelatine. 7 r 1 v 7.. .The filmof .cl aim v1 wherein .thesaid filinforming plastic .is .a -partially hydrolyzedpoly- .vinylacetate. v I

8.. ,The film of claiml wherein thesaid-film- .ifonning .plastic vis hydroxymethyl cellulose.

WILLIAMOMNEKN-L REFERENCES CITED The following references are of lti'ecord in nthe UNITED STATES-PATENTS Number Name 7 Date 2,069,773 Reid Feb. 9, 1937 2,099,441 Heckert Nov. 16,1937 2,199,927 Underwood May 7, 1940 2,434,496 Houtman 1 Jan. 13, 1948 

1. AN IMPROVED ULTRAVIOLET LIGHT ABSORBING FILM COMPRISING A FILM-FORMING PLASTIC SOLUBLE IN AN AQUEOUS MEDIUM HAVING A PH OF 5 TO 9.5 AND A SALT OF A SULFONIC ACID, WHICH SULFONIC ACID HAS THE FORMULA: 